The present invention relates to a vehicle seat with a side airbag apparatus.
The side airbag apparatus is widely known as an apparatus that protects an occupant seated in a vehicle seat when an impact is applied to the seat from a side, for example, due to a side collision. A typical side airbag apparatus includes an inflator and an airbag, which is inflated with inflation gas supplied from the inflator. The inflator and the airbag are installed in the outer side of the seat back (backrest) of a vehicle seat.
One known form of the side airbag apparatus includes an airbag having a main inflation portion (a main airbag) and an auxiliary inflation portion (an auxiliary airbag) as disclosed in, for example, Japanese Laid-Open Patent Publications No. 2009-23490 and No. 2009-23494. The names of members inside the parentheses represent the names of members used in Japanese Laid-Open Patent Publications No. 2009-23490 and No. 2009-23494.
The main inflation portion is inflated with inflation gas supplied from the inflator and projects from the seat back to be deployed forward between the occupant and a side wall of the vehicle. Prior to the deployment of the main inflation portion outside the seat back, the auxiliary inflation portion is inflated inside the seat back with inflation gas to push the occupant toward the inner side. The inflated auxiliary inflation portion pushes part of the seat back that is forward of the auxiliary inflation portion so that the part bulges toward the inner side and diagonally forward. The bulging part pushes the back of the occupant leaning against the seat back, thereby moving the occupant toward the inner side. This enlarges the space between the occupant and the side wall, thereby facilitating forward deployment and inflation of the main inflation portion.
If, for example, installed in the vehicle seat disclosed in Japanese Laid-Open Patent Publication No. 2011-105126, the above described airbag apparatus has the following drawbacks.
The vehicle seat disclosed in Japanese Laid-Open Patent Publication No. 2011-105126 includes a seat frame, which constitutes the framework of the seat back. The seat frame includes a pressure receiving plate (a plastic plate), which is arranged at the center in the vehicle width direction, and an outer frame portion, which is separated from and surrounds the pressure receiving plate. The pressure receiving plate is used to stably support the back of the occupant seated in the vehicle seat. The names of members inside the parentheses represent the names of members used in Japanese Laid-Open Patent Publications No. 2011-105126.
If the above described airbag apparatus is employed in the vehicle seat of the publication, the airbag and the inflator, which form the main part of the side airbag apparatus, are installed in the outer side section of the seat back. When the inflator discharges inflation gas, the main inflation portion and the auxiliary inflation portion are respectively inflated. The inflation of the auxiliary inflation portion takes place on the front side of the pressure receiving plate in the seat back. At this time, the auxiliary inflation portion is pushed from the front by the occupant and inflated rearward and may enter the gap between the outer frame portion and the pressure receiving plate in the seat frame. This reduces the reaction force of the auxiliary inflation portion that acts to push the part of the seat back that is forward of the auxiliary inflation portion and causes the part to bulge toward the inner side and diagonally forward. As a result, the movement of the occupant toward the inner side and the enlargement of the space between the occupant and the side wall may be insufficient.